Enhanced Collimation - Meade LightBridge Plus Instruction Manual

Truss tube dobsonian telescopes

Hide thumbs

Table Of Contents

Table of Contents

Enlarged version

Any deviation from concentricity of any of these

telescope parts with the eye requires adjustments

to the secondary mirror-holder (Fig. 23) and/or the

primary mirror cell (Fig. 24), as described below.

2. Secondary mirror-vane adjustments: If the

secondary mirror (1, Fig. 26) is above or below

center within the draw tube, thread inward one of

the spider vane adjustment/lock knobs (44, Fig.

5) while unthreading the opposite knobs. Only

make adjustments to two knobs at a time until the

secondary mirror appears as in Fig. 27.

3. Secondary mirror-holder adjustments:

If the secondary mirror (1, Fig. 27) is left or right

of center within the draw tube, adjust the center

phillips head screw on the secondary mirror holder

to move the secondary mirror into position. Do not

unthread the center mounting screw too much

or the secondary mirror holder can fall off of the

spider vanes completely.

If the secondary mirror (1, Fig. 27) is centered in

the focuser draw tube (2, Fig. 27), but the primary

mirror is only partially visible in the reflection (3,

Fig. 27), the three "+" (Phillips head) secondary

mirror-tilt screws (2, Fig. 23) should be slightly

unthreaded to the point where the secondary

mirror-holder (3, Fig. 23) can rotate about its axis

parallel to the main tube. Grasp the secondary

mirror-holder (avoid touching the mirror surface!)

with your hand and rotate it until, looking through

the draw tube, you can see the primary mirror

centered as well as possible in the reflection of the

secondary mirror. With the rotation of the secondary

mirror-holder at this best-possible position, thread

in the three Phillips head screws (2, Fig. 23) to lock

the rotational position. Then, if necessary, make

adjustments to these three Phillips head screws to

refine the tilt-angle of the secondary mirror, until

the entire primary mirror can be seen centered

within the secondary mirror's reflection. With the

secondary mirror thus aligned the image through

the draw tube appears as in Fig. 28.

4. Primary mirror adjustments: If the secondary

mirror (1, Fig. 28) and the reflection of the primary

mirror (2, Fig. 28) appear centered within the

draw tube (3, Fig. 28), but the reflection of your

eye and the reflection of the secondary mirror (4,

Fig. 28) appear off-center, then the primary mirror

tilt requires adjusting. Use the primary mirror

collimation adjustment knobs to tilt the mirror.

Note: Always loosen the collimation lock knobs

before adjusting the primary mirror tilt.

The primary mirror-tilt screws are located behind

the primary mirror, at the lower end of the main

tube. See Fig. 29.

Before adjusting the primary mirror-tilt screws, first

unscrew by several turns the three primary mirror

lock screws (Fig. 29) which are also located on the

rear surface of the primary mirror cell and which

alternate around the cell's circumference with the

three adjustment knobs. Then by trial and error turn

the primary mirror adjustment knobs (Fig. 29) until

you develop a feel for which way to turn each knob

to center the reflection of your eye in the draw tube.

(An assistant is helpful in this operation.) With your

eye centered as shown in Fig. 25, turn the three

primary mirror lock knobs (Fig. 29) to re-lock the

tilt-angle of the primary mirror. The telescope's

optical system is now aligned. This collimation

should be checked after each optical tube setup

and from time to time, with small adjustments (per

steps 1, 2, 3, and/or 4, above) effected as required

to keep the optics well-aligned.

Collimation lock

knobs

(without springs)

Figure 29